1 Field of the Invention
This invention relates to an ester compound containing optically active alkyl or alkoxy group in the molecule, which is useful as a ferroelectric liquid crystal compound.
2 Description of the Prior Art:
Methods of displaying with a liquid crystal display element widely used today may be classified into those of twisted nematic (TN) and dynamic scattering (DS) types. These methods involve nematic liquid crystal cells comprising nematic liquid crystals as the main component. One of the disadvantages of conventional nematic liquid crystal cells is that their response speed is of the order of several milliseconds at the most, which cosiderably restrict the application thereof. It has been recently found that a higher response speed can be obtained by using a smectic liquid crystal cell.
It has been disclosed that some optically active smectic liquid crystals show ferroelectricity and thus the application thereof has been eagerly expected. An example of the ferroelectric liquid crystals is 2-methylbutyl-4-(4-n-decyloxy-benzylidenamino) cinnamate which will be abbreviated to DOBAMBC hereinafter. This compound is characterized by showing a ferroelectricity in the chiral smectic phase which will be abbreviated to Sc* phase hereinafter.
Since it was found that a DOBAMBC film cell had a high response speed of the order of a microsecond, this ferroelectric liquid crystal compound has attracted public attention as a material available not only in display devices of, for example, a liquid crystal TV but also in various optoelectronics devices such as a photoprinter head, an optical Fourier-transform element and a light valve.
However the DOBAMBC has not been utilized in practice yet, since it is chemically unstable because of the presence of a Schiff base structure therein.
Recently, optically active ester compounds such as alkoxybiphenylcarboxylic acid alkoxyphenyl esters and alkoxybenzoic acid alkoxybiphenyl esters which contain an optically active alkoxy group such as 2-methylbutoxy, 6-methyloctoxy and 1-methylheptoxy in the molecule have been proposed as a ferroelectric liquid crystal compound.
However, these ester compounds are available only within a restricted range of temperature.